Diagram

Design & Prerequisites

With OTV, it is extremely important to ensure that you have a good network design and that your network meets all the pre-requisites to support OTV deployment:

Network design - have clear understanding of boundaries between:

L2 and L3 in each site

Functional data center layers (access, aggregation, core) in each site

Each site and provider / WAN network.

Ensure that there is L3 connectivity between all the sites.

Ensure that provider / WAN network supports IP Multicast or decide which OTV edge device will act as adjacency server (check with DCBU on feature availability post-FCS of OTV). For IP Multicast, ASM / Bidir need to be supported for control plane communication and SSM for any data multicast traffic between sites.

Identify number and placement of OTV edge devices in each site. Remember that at FCS, L3 gateway and OTV edge for a VLAN can not reside on the same logical device. This may require provisioning a VDC off aggregation layer N7Ks to serve as OTV edge device.

Identify internal interface L2 connectivity of each OTV edge device to aggregation layer. Will L2 connection be single-homed to one aggregation switch, multi-homed using STP or multi-homed with VPC?

Identify L3 connectivity of each OTV edge device to the provider network / WAN. Will L3 connection be single-homed or multi-homed connecting to 2 or more WAN endpoints? In multi-homed case, consider that there can only be 1 join-interface and based on that , decide whether join interface will be a MCEC or one of the uplinks. If only one of uplinks is used as join-interface, other one can be used for unicast traffic loadbalancing between sites.

Decide which VLANs will be extended and how many Overlays will be used for that. Most simple design can just use 1 Overlay, however a more complex design can be used with VLANs split between Overlays for loadbalancing.

Note if any of VLANs being extended are running FHRPs on L3 gateways. If multiple sites have FHRP running for VLAN being extended, HSRP localization feature (post-FCS) or other workarounds should be used!

Designate a site VLAN to be used for communication between 2 OTV edge devices in a single site. In case sites ever get merged, it is recommended to use same VLAN ID to provision a site VLAN in each site, regardless whether it currently has 1 or 2 edge devices.

Procedures

These procedures will outline the configuration necessary for OTV to be enabled in each site. It is assumed that pre-requisites such as L3 connectivity and Multicast have already been configured and best practices for those have been used.

Enable OTV feature.

Create a logical Overlay interface.

Configure IGMP v3 on join-interface.

Configure join-interface (you will get a warning about IGMP v3 regardless of completion of STEP 3).

Configure multicast groups for control traffic between OTV sites and for any multicast data traffic between OTV sites.

Configure VLANs to be extended over this Overlay.

Repeat steps 2-6 for any additional Overlays that need to be configured.

Configure site VLAN and make sure that between 2 OTV edge devices in a single site, a L2 connectivity exists through that VLAN.

Verify proper OTV operation.

Examples

Following contains configuration example from one of OTV edge devices: